Method and apparatus for investigation of projectile flight

ABSTRACT

A DEVICE COMPRISING TWO INTERSECTING PLANAR MIRRORS IS PLACED ADJACENT TO THE FLIGHT PATH OF A PROJECTILE WITH THE LINE OF INTERSECTION OF THE TWO MIRRORS NORMAL TO THE LINE OF SIGHT OF A CAMERA. THE ANGLE AT WHICH THE MIRRORS INTERSECT IS CHOSEN TO PROVIDE FIVE SEPARATE IMAGES VISIBLE IN A SINGLE PHOTOGRAPH MADE OF THE PROJECTILE BY THE CAMERA.

.,-06-O6-72 QR June 6, 1972 c. GRIFFIN 3,667,847

METHOD AND APPARATUS FOR INVESTIGATION OF PROJECTILE FLIGHT Filed Aug. 24, 1970 TOP I BOTTOM REAR REF. LINE TOP-REAR BOTTOM AQ, 5. 0&- 0.2 Q REF. LINE D n D 9 g D Q 1:: g

I; E g F. (5.? H.

g REF. LINE g i Q Q a Q g y V I FIG, 3 WILLlAM Cv GRlFFlN I? ROY MTLLER ATTORNEY.

GERALD F BAKER AGENT.

United States Patent 3,667,847 METHOD AND APPARATUS FOR INVESTIGATION OF PROJECTILE FLIGHT William C. Griflin, Ridgecrest, Calif., assignor to the United States of America as represented by the Secretary of the Navy Filed Aug. 24, 1970, Ser. No. 66,368 Int. Cl. G01b 19/34 US. Cl. 356-138 1 Claim ABSTRACT OF THE DISCLOSURE A device comprising two intersecting planar mirrors is placed adjacent to the flight path of a projectile with the line of intersection of the two mirrors normal to the line of sight of a camera. The angle at which the mirrors intersect is chosen to provide five separate images visible in a single photograph made of the projectile by the camera.

BACKGROUND OF THE INVENTION Prior attempts to view more than one side of a projectile in flight has involved a plurality of cameras spaced around the field of view. Solving the problems inherent in synchronizing the cameras and spacing them so that a plurality of views of a projectile could cover all sides of the projectile at the same time proved to be practically impossible under these prior systems.

SUMMARY OF THE INVENTION The system according to the present invention records five images for 360-degree viewing of objects in flight and provides one reference line for measurement. The device used comprises two first-surface mirrors joined at a 73- degree angle. Characteristic signature patterns produced by the various conditions of pitch and yaw are recorded on film, enabling data reduction personnel to establish projectile attitudes at a point on the flight line. The signature is different for each composite attitude. When he projectile yaws toward the camera, a fanning out is apparent and, when the yaw is away from the camera, the inverse is true. Other characteristic signatures are provided when the object is in a pitch-up or pitch-down attitude, with or without yaw.

The multiple-image technique according to the invention, thus, provides the following information using only one camera and a simple lighting system:

(.1) Attitude of the projectile pitch and yaw.

(2) Deviation from boresight point up and down, as well as in or off range.

(3) Coincident condition of all 360 degrees of the projectile surface during flight.

(4) Spin. As all degrees of rotation are covered, onefifth the usual camera framing rate can be used, provided exposure time is not increased.

This technique can also be used to obtain accurate velocity data and attitude change as related to time and distance by using two multiple-image devices separated by a precisely known distance, each having its own camera and coded timing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIG. 1 is a schematic perspective view of a typical system according to the invention;

FIG. 2 is a graphical representation of the photographic signature of a projectile in true normal flight; and

FIG. 3 is a composite of several selected graphically presented signatures of projectiles in other than true normal flight.

3,667,847; Patented June 6, 1972 ice The system 10 shown in FIG. 1 generally comprises a multiple image device 12, means 20 for firing a projectile and necessary lighting and cameras to record desired events.

As shown in FIG. 1, the multiple image device 12 comprises two first-surface mirrors 13, 15 placed at a 73- degree angle to each other with the intersection of the two mirrors in a plane which is approximately parallel to the surface of the earth and includes the flight line. Powerful lights 1-6, 18 are focused on the area as shown in FIG. 11 and a camera 30 is placed in position approximately in the position of the camera which took the photograph grapically illustrated in FIG. 2. When the projectile is fired, the high speed camera 30 is started and at least a few frames of the film will be in action as the projectile passes the device 12. At least one frame will show the projectile in place before the multiple image device as shown in FIG. 2.

A high speed camera 30 is placed with its line of sight orthogonally intersecting said line of fire and said line of intersection median of frame 14.

When a projectile from gun 20 passes the device 14 in true flight, one or more frames of the film in camera 30 will record a five image composite photograph similar to that illustrated in FIG. 2 on the drawing. The projectile is represented in FIG. 2, however, as being slightly low in elevation as evidenced by the spacing between the center line of the FRONT image and the REF. LINE which is the line of intersection of mirrors 13, 15.

In FIG. 2, the FRONT image is obviously the direct view image of the projectile as viewed by camera 30. The TOP and BOTTOM views are primary reflections of the projectile from mirrors 13 and 15, respectively, and the TOP and BOTTOM REAR views are secondary reflections.

When the projectile is photographed in system 10, abnormal flight patterns may be observed as shown in FIG. 3. The views at A and B illustrate a slight yaw of the projectile with the nose toward the camera and away from the camera, respectively.

Tilting of the projectile at the time the photograph is made will result in patterns shown in views C and D and combinations of pitch and yaw are represented in views E through H as follows.

(E) pitch up with yaw nose toward camera.

(F) pitch up with yaw nose away from camera. (G) pitch down with yaw nose toward camera. (H) pitch down with yaw nose away from camera.

invention, provides the following information using only a fanning out is apparent and, when the yaw is away from the camera, the inverse is true.

The multiple-image system, according to the present one camera and a simple lighting system:

Note that, when the projectile yaws toward the camera,

(1) Attitude of the projectile (pitch and yaw).

(2) Deviation from boresight point up and down, as well as in or off range.

(3) 360-degree view of the projectile surface during flight.

(4) Spin. As all degrees of rotation are covered, onefifth the usual camera framing rate can be used, provided exposure time is not increased.

This technique can also be used to obtain accurate velocity data and attitude change as related to time and distance by using two multiple-image devices separated by a precisely known distance, each having its own camera and coded timing.

3 a, What is claimed is: References (Iited Apparatus for investigating projectile flight charac- UNITED STATES'PA-TENTS tenstics compnsmg a multlple image dev1ce ad aCent to the line of flight of said projectile and means photo- 505,127 9/1893 Ranger 350 299 X graphically recording instantaneous images of said pro- 5 jectile and of the images reflected by said multiple image RONALD WIBERT Pnmary Exammer device; said multiple image device comprising two plane, 0, B. CHEW IL-Assistant Examiner first surface mirrors intersecting at an angle of 73 degrees in a line parallel to said flight line directly opposite said U.S. Cl. X.R. means for recording. 10 95-ll; 350299 Patent No. 3,667 ,847

UNITED STATES PATENT OFFICE CERTIFIQATE oreottneerton 6 June 1972 WILLIAM C GRIFFIN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected in column 2 lines 53-53 as shown below:

Note that, when the projectile yaws toward the camera a fanning out is apparent and, when the yaw is away 55 front the camera, the inverse is true.

I The multiple-hinge system, according to the present invention, provides the following information ttriinw only one camera and a simple lighting system: J

Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M.FLE'ICHE1R,J'R.- ROBERT GOT'I'SCHALK Commissioner of Patents Attesting Officer 

